// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// A set of utility functions to perform WSOLA.

#ifndef MEDIA_FILTERS_WSOLA_INTERNALS_H_
#define MEDIA_FILTERS_WSOLA_INTERNALS_H_

#include <utility>

#include "media/base/media_export.h"

namespace media {

class AudioBus;

namespace internal {

    typedef std::pair<int, int> Interval;

    // Dot-product of channels of two AudioBus. For each AudioBus an offset is
    // given. |dot_product[k]| is the dot-product of channel |k|. The caller should
    // allocate sufficient space for |dot_product|.
    MEDIA_EXPORT void MultiChannelDotProduct(const AudioBus* a,
        int frame_offset_a,
        const AudioBus* b,
        int frame_offset_b,
        int num_frames,
        float* dot_product);

    // Energies of sliding windows of channels are interleaved.
    // The number windows is |input->frames()| - (|frames_per_window| - 1), hence,
    // the method assumes |energy| must be, at least, of size
    // (|input->frames()| - (|frames_per_window| - 1)) * |input->channels()|.
    MEDIA_EXPORT void MultiChannelMovingBlockEnergies(const AudioBus* input,
        int frames_per_window,
        float* energy);

    // Fit the curve f(x) = a * x^2 + b * x + c such that
    //   f(-1) = y[0]
    //   f(0) = y[1]
    //   f(1) = y[2]
    // and return the maximum, assuming that y[0] <= y[1] >= y[2].
    MEDIA_EXPORT void QuadraticInterpolation(const float* y_values,
        float* extremum,
        float* extremum_value);

    // Search a subset of all candid blocks. The search is performed every
    // |decimation| frames. This reduces complexity by a factor of about
    // 1 / |decimation|. A cubic interpolation is used to have a better estimate of
    // the best match.
    MEDIA_EXPORT int DecimatedSearch(int decimation,
        Interval exclude_interval,
        const AudioBus* target_block,
        const AudioBus* search_segment,
        const float* energy_target_block,
        const float* energy_candid_blocks);

    // Search [|low_limit|, |high_limit|] of |search_segment| to find a block that
    // is most similar to |target_block|. |energy_target_block| is the energy of the
    // |target_block|. |energy_candidate_blocks| is the energy of all blocks within
    // |search_block|.
    MEDIA_EXPORT int FullSearch(int low_limit,
        int hight_limimit,
        Interval exclude_interval,
        const AudioBus* target_block,
        const AudioBus* search_block,
        const float* energy_target_block,
        const float* energy_candidate_blocks);

    // Find the index of the block, within |search_block|, that is most similar
    // to |target_block|. Obviously, the returned index is w.r.t. |search_block|.
    // |exclude_interval| is an interval that is excluded from the search.
    MEDIA_EXPORT int OptimalIndex(const AudioBus* search_block,
        const AudioBus* target_block,
        Interval exclude_interval);

    // Return a "periodic" Hann window. This is the first L samples of an L+1
    // Hann window. It is perfect reconstruction for overlap-and-add.
    MEDIA_EXPORT void GetSymmetricHanningWindow(int window_length, float* window);

} // namespace internal

} // namespace media

#endif // MEDIA_FILTERS_WSOLA_INTERNALS_H_
